The program DCDT+ is a Windows implementation of Walter Stafford's DCDT algorithm integrated with non-linear curve fitting to derive sedimentation and diffusion coefficients (or molecular mass) for up to 5 components in a mixture, using a user interface similar to that in SVEDBERG. It comes with context-sensitive Help, tutorials, and "how-to" guides. Current versions of this program can be downloaded from John Philo’s software site, www.jphilo.mailway.com . The source code for his programs is archived on this site at http://philo.rasmb.org/software/